Effects of intradermal lignocaine and mepivacaine on human cutaneous circulation in areas with histamine-induced neurogenic inflammation.

The vasoconstrictive potencies of lignocaine and mepivacaine were studied in human skin. Lignocaine 0.5%, 0.25% mepivacaine (both plain and mixed with adrenaline or ornipressin), and saline (control) were injected intradermally into skin areas with enhanced perfusion (1% histamine prick). Flux was determined by scanning laser Doppler flowmetry and the size of any eventual pallor was measured. The artificially enhanced flux was increased further by saline, but not altered by the local anaesthetics. Mepivacaine produced a small pallor. Both vasoconstrictors reduced flux significantly and produced a larger pallor. We conclude that both local anaesthetics have only a mild constrictive effect on precapillary vessels. Mepivacaine has, additionally, a constrictor effect on the postcapillary vascular bed, causing pallor. An effective precapillary constriction which reduces the capillary clearance of both local anaesthetics can be achieved only by addition of a vasoconstrictor.